Crth2 antagonists

ABSTRACT

The following compounds are CRTH2 antagonists, useful in treatment of respiratory disease: [3-(2,4-dichlorophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]acetic acid, [6-fluoro-3-(2-fluoro-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]acetic acid, [6-fluoro-3-(4-methanesulfonyl-2-trifluoromethylphenylsulfanyl)-2-methylindolizin-1-yl]acetic acid, (R)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionic acid, [3-(4-ethanesulfonylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]acetic acid, (S)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionic acid, ethanesulfonylaminobenzenesulfonyl)-6-fluoro-2-methyiindolizin-1-yl]acetic acid, [7-chloro-6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]acetic acid, [3-(2-chloro-4-methanesulfonylphenylsulfanyl)-7-cyano-2-methylindolizin-1-yl]acetic acid, [6-cyano-3-(4-methanesulfonylbenzyl)-2-methylindolizin-1-yl]acetic acid, [3-(4-chlorobenzyl)-7-cyano-2-methylindolizin-1-yl]acetic acid, [6-cyano-3-(6-fluoroquinolin-2-yl-methyl)-2-methylindolizin-1-yl]acetic acid, [6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]acetic acid, [7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]acetic acid, [3-(4-bromophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]acetic acid, and [3-(4-cyclopropylsulfamoylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]acetic acid.

This invention relates to specific indolizine compounds which areligands of the CRTH2 receptor (Chemoattractant Receptor-homologousmolecule expressed on T Helper cells type 2), and their use in thetreatment of diseases responsive to modulation of CRTH2 receptoractivity, principally diseases having a significant inflammatorycomponent.

BACKGROUND TO THE INVENTION

Mast cells are known to play an important role in allergic and immuneresponses through the release of a number of mediators, such ashistamine, leukotrienes, cytokines, prostaglandin D₂, etc (Boyce;Allergy Asthma Proc., 2004, 25, 27-30). Prostaglandin D₂ (PGD₂) is themajor metabolite produced by the action of cyclooxygenase on arachadonicacid by mast cells in response to allergen challenge (Lewis et al; J.Immunol., 1982, 129, 1627-1631). It has been shown that PGD₂ productionis increased in patients with systemic mastocytosis (Roberts; N. Engl.J. Med., 1980, 303, 1400-1404), allergic rhinitis (Naclerio et al; Am.Rev. Respir. Dis., 1983, 128, 597-602; Brown et al; Arch. Otolarynol.Head Neck Surg., 1987, 113, 179-183; Lebel et al; J. Allergy Clin.Immunol., 1988, 82, 869-877), bronchial asthma (Murray et al; N. Engl.J. Med., 1986, 315, 800-804; Liu et al; Am. Rev. Respir. Dis., 1990,142, 126-132; Wenzel et al; J. Allergy Clin. Immunol., 1991, 87,540-548), and urticaria (Heavey et al; J. Allergy Clin. Immunol., 1986,78, 458-461). PGD₂ mediates it effects through two receptors, the PGD₂(or DP) receptor (Boie et al; J. Biol. Chem., 1995, 270, 18910-18916)and the chemoattractant receptor-homologous molecule expressed on Th2(or CRTH2) (Nagata et al; J. Immunol., 1999, 162, 1278-1289; Powell;Prostaglandins Luekot. Essent. Fatty Acids, 2003, 69, 179-185).Therefore, it has been postulated that agents that antagonise theeffects of PGD₂ at its receptors may have beneficial effects in a numberof disease states.

The CRTH2 receptor has been shown to be expressed on cell typesassociated with allergic inflammation, such as basophils, eosinophils,and Th2-type immune helper cells (Hirai et al; J. Exp. Med., 2001, 193,255-261). The CRTH2 receptor has been shown to mediate PGD₂-mediatedcell migration in these cell types (Hirai et al; J. Exp. Med., 2001,193, 255-261), and also to play a major role in neutrophil andeosinophil cell recruitment in a model of contact dermatitis (Takeshitaet al; Int. Immunol., 2004, 16, 947-959). Ramatroban{(3R)-3-[(4-fluorophenyl)sulphonylamino]-1,2,3,4-tetrahydro-9H-carbazole-9-propanoicacid}, a dual CRTH2 and thromboxane A₂ receptor antagonist, has beenshown to attenuate these responses (Sugimoto et al; J. Pharmacol. Exp.Ther., 2003, 305, 347-352; Takeshita et al; op. cit.). The potential ofPGD₂ both to enhance allergic inflammation and induce an inflammatoryresponse has been demonstrated in mice and rats. Transgenic mice overexpressing PGD₂ synthase exhibit an enhanced pulmonary eosinophilia andincreased levels of Th2 cytokines in response to allergen challenge(Fujitani et al, J. Immunol., 2002, 168, 443-449). In addition,exogenously administered CRTH2 agonists enhance the allergic response insensitised mice (Spik et al; J. Immunol., 2005, 174, 3703-3708). In ratsexogenously applied CRTH2 agonists cause a pulmonary eosinophilia but aDP agonist (BW 245C) or a TP agonist (I-BOP) showed no effect (Shirashiet al; J. Pharmacol. Exp Ther., 2005, 312, 954-960). These observationssuggest that CRTH2 antagonists may have valuable properties for thetreatment of diseases mediated by PGD₂.

Our copending application PCT/GB2006/002341 relates to CRTH2 antagonistcompounds of formula (I) and salts, N-oxides, hydrates and solvatesthereof:

wherein

R₁, R₂, R₃ and R₄ each independently are hydrogen, C₁-C₆alkyl, fully orpartially fluorinated C₁-C₆alkyl, halo, —S(O)_(n)R₁₀, —SO₂N(R₁₀)₂,—N(R₁₀)₂, —C(O)N(R₁₀)₂, —NR₁₀C(O)R₉, —CO₂R₁₀, —C(O)R₉, —NO₂, —CN or—OR₁₁;

-   -   wherein each R₉ is independently C₁-C₆alkyl, aryl, heteroaryl;    -   R₁₀ is independently hydrogen, C₁-C₆alkyl, aryl, or heteroaryl;    -   R₁₁ is hydrogen, C₁-C₆alkyl, fully or partially fluorinated        C₁-C₆alkyl or a group —SO₂R₉;    -   n is 0, 1 or 2;

R₅ is C₁-C₆alkyl, fully or partially fluorinated C₁-C6alkyl,C₁-C6alkenyl, C₁-C₆alkynyl, optionally substituted aryl, or optionallysubstituted heteroaryl;

R₆ is hydrogen, C₁-C₆alkyl or fully or partially fluorinated C₁-C₆alkyl;

R₇ and R₈ are independently hydrogen or C₁-C₆alkyl, or R₇ and R₈together with the atom to which they are attached form a cycloalkylgroup; and

X is —CHR₆—, —S(O)_(n)—, —NR₆SO₂— or —SO₂NR₆— wherein n is 0, 1 or 2,

PROVIDED THAT when X is —CH₂—, R₆ is methyl and R₅ is 4-chlorophenyl,then R₁, R₂, R₃, R₄, R₇ and R₈ are not all hydrogen.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a group of specific compounds fallingwithin the scope of, but not specifically disclosed in our copendingapplication PCT/GB2006/002341 referred to above.

The invention provides a compound selected from the group consisting of

[3-(2,4-dichlorophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid,

[6-fluoro-3-(2-fluoro-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,

[6-fluoro-3-(4-methanesulfonyl-2-trifluoromethylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,

(R)2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid,

(S)2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid,

[3-(4-ethanesulfonylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid,

ethanesulfonylaminobenzenesulfonyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid,

[7-chloro-6-fluoro-3-(4-methanesufonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,

[3-(2-chloro-4-methanesulfonylphenylsulfanyl)-7-cyano-2-methylindolizin-1-yl]aceticacid,

[6-cyano-3-(4-methanesulfonylbenzyl)-2-methylindolizin-1-yl]acetic acid,

[3-(4-chlorobenzyl)-7-cyano-2-methylindolizin-1-yl]acetic acid,

[6-cyano-3-(6-fluoroquinolin-2-ylmethyl)-2-methylindolizin-1-yl]aceticacid,

[6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,

[7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,

[3-(4-bromophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]acetic acid,

[3-(4-cyclopropylsulfamoylphenylsufanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid, and salts, N-oxides, hydrates and solvates thereof.

Compounds with which the invention is concerned are CRTH2 receptorantagonists.

A second aspect of the invention is a pharmaceutical compositioncomprising a compound of the invention in admixture with apharmaceutically acceptable carrier or excipient.

A third aspect of the invention is a compound of the invention for usein therapy.

A fourth aspect of the invention is the use of a compound of theinvention in the manufacture of a medicament for the treatment of adisease in which a CRTH2 antagonist can prevent, inhibit or amelioratethe pathology and/or symptomatology of the disease. Such diseasesinclude asthma, chronic obstructive pulmonary disease, rhinitis,allergic airway syndrome, or allergic rhinobronchitis, as well as atopicand non-atopic dermatitis, Crohn's disease, ulcerative colitis, andirritable bowel disease.

A fifth aspect of the invention is a method for treating a disease in apatient in which a CRTH2 antagonist can prevent, inhibit or amelioratethe pathology and/or symptomatology of the disease, which methodcomprises administering to the patient a therapeutically effectiveamount of a compound of the invention.

In particular, compounds with which the invention is concerned areuseful in the treatment of disease associated with elevated levels ofprostaglandin D2 (PGD2) or one or more active metabolites thereof.

Examples of such diseases include asthma, rhinitis, allergic airwaysyndrome, allergic rhinobronchitis, bronchitis, chronic obstructivepulmonary disease (COPD), nasal polyposis, sarcoidosis, farmer's lung,fibroid lung, cystic fibrosis, chronic cough, conjunctivitis, atopic andnon-atopic dermatitis, Alzheimer's disease, amyotrophic lateralsclerosis, AIDS dementia complex, Huntington's disease, frontotemporaldementia, Lewy body dementia, vascular dementia, Guillain-Barresyndrome, chronic demyelinating polyradiculoneurophathy, multifocalmotor neuropathy, plexopathy, multiple sclerosis, encephalomyelitis,panencephalitis, cerebellar degeneration and encephalomyelitis, CNStrauma, migraine, stroke, rheumatoid arthritis, ankylosing spondylitis,Behcet's Disease, bursitis, carpal tunnel syndrome, inflammatory boweldisease, Crohn's disease, ulcerative colitis, dermatomyositis,Ehlers-Danlos Syndrome (EDS), fibromyalgia, myofascial pain,osteoarthritis (OA), osteonecrosis, psoriatic arthritis, Reiter'ssyndrome (reactive arthritis), sarcoidosis, scleroderma, Sjogren'sSyndrome, soft tissue disease, Still's Disease, tendinitis,polyarteritis Nodossa, Wegener's Granulomatosis, myositis (polymyositisdermatomyositis), gout, atherosclerosis, lupus erythematosus, systemiclupus erythematosus (SLE), type I diabetes, nephritic syndrome,glomerulonephritis, acute and chronic renal failure, eosinophiliafascitis, hyper IgE syndrome, sepsis, septic shock, ischemic reperfusioninjury in the heart, allograft rejection after transplantations, andgraft versus host disease.

However, the compounds with which the invention is concerned areprimarily of value for the treatment of asthma, chronic obstructivepulmonary disease, rhinitis, allergic airway syndrome, or allergicrhinobronchitis, as well as atopic and non-atopic dermatitis, Crohn'sdisease, ulcerative colitis, and irritable bowel disease.

As used herein the term “salt” includes base addition, acid addition andquaternary salts. Compounds of the invention which are acidic can formsalts, including pharmaceutically acceptable salts, with bases such asalkali metal hydroxides, e.g. sodium and potassium hydroxides; alkalineearth metal hydroxides e.g. calcium, barium and magnesium hydroxides;with organic bases e.g. N-methyl-D-glucamine, cholinetris(hydroxymethyl)amino-methane, L-arginine, L-lysine, N-ethylpiperidine, dibenzylamine and the like. Specific salts with basesinclude the benzathine, calcium, diolamine, meglumine, olamine,potassium, procaine, sodium, tromethamine and zinc salts. Thosecompounds of the invention which are basic can form salts, includingpharmaceutically acceptable salts with inorganic acids, e.g. withhydrohalic acids such as hydrochloric or hydrobromic acids, sulphuricacid, nitric acid or phosphoric acid and the like, and with organicacids e.g. with acetic, tartaric, succinic, fumaric, maleic, malic,salicylic, citric, methanesulphonic, p-toluenesulphonic, benzoic,benzenesunfonic, glutamic, lactic, and mandelic acids and the like.

Use of prodrugs, such as esters, of compounds with which the inventionis concerned is also part of the invention. “Prodrug” means a compoundwhich is convertible in vivo by metabolic means (e.g. by hydrolysis,reduction or oxidation) to a compound of formula (I). For example anester prodrug of a compound of formula (I) may be convertible byhydrolysis in vivo to the parent molecule. Suitable esters of compoundsof formula (I) are for example acetates, citrates, lactates, tartrates,malonates, oxalates, salicylates, propionates, succinates, fumarates,maleates, methylene-bis-β-hydroxynaphthoates, gentisates, isethionates,di-p-toluoyltartrates, methanesulphonates, ethanesulphonates,benzenesulphonates, p-toluene-sulphonates, cyclohexylsulphamates andquinates. Examples of ester prodrugs are those described by F. J.Leinweber, Drug Metab. Res., 1987, 18, 379. As used in herein,references to the compounds of formula (I) are meant to also include theprodrug forms.

Compositions

As mentioned above, the compounds with which the invention is concernedare CRTH2 receptor antagonists, and are useful in the treatment ofdiseases which benefit from such modulation. Examples of such diseasesare referred to above, and include asthma, rhinitis, allergic airwaysyndrome, and allergic rhinobronchitis.

It will be understood that the specific dose level for any particularpatient will depend upon a variety of factors including the activity ofthe specific compound employed, the age, body weight, general health,sex, diet, time of administration, route of administration, rate ofexcretion, drug combination and the severity of the particular diseaseundergoing treatment. Optimum dose levels and frequency of dosing willbe determined by clinical trial, as is required in the pharmaceuticalart. In general, the daily dose range will lie within the range of fromabout 0.001 mg to about 100 mg per kg body weight of a mammal, often0.01 mg to about 50 mg per kg, for example 0.1 to 10 mg per kg, insingle or divided doses. On the other hand, it may be necessary to usedosages outside these limits in some cases.

The compounds with which the invention is concerned may be prepared foradministration by any route consistent with their pharmacokineticproperties. Orally administrable compositions may be in the form oftablets, capsules, powders, granules, lozenges, liquid or gelpreparations, such as oral, topical, or sterile parenteral solutions orsuspensions. Tablets and capsules for oral administration may be in unitdose presentation form, and may contain conventional excipients such asbinding agents, for example syrup, acacia, gelatin, sorbitol,tragacanth, or polyvinyl-pyrrolidone; fillers for example lactose,sugar, maize-starch, calcium phosphate, sorbitol or glycine; tablettinglubricant, for example magnesium stearate, talc, polyethylene glycol orsilica; disintegrants for example potato starch, or acceptable wettingagents such as sodium lauryl sulphate. The tablets may be coatedaccording to methods well known in normal pharmaceutical practice. Oralliquid preparations may be in the form of, for example, aqueous or oilysuspensions, solutions, emulsions, syrups or elixirs, or may bepresented as a dry product for reconstitution with water or othersuitable vehicle before use. Such liquid preparations may containconventional additives such as suspending agents, for example sorbitol,syrup, methyl cellulose, glucose syrup, gelatin hydrogenated ediblefats; emulsifying agents, for example lecithin, sorbitan monooleate, oracacia; non-aqueous vehicles (which may include edible oils), forexample almond oil, fractionated coconut oil, oily esters such asglycerine, propylene glycol, or ethyl alcohol; preservatives, forexample methyl or propyl p-hydroxybenzoate or sorbic acid, and ifdesired conventional flavouring or colouring agents.

For topical application to the skin, the drug may be made up into acream, lotion or ointment. Cream or ointment formulations which may beused for the drug are conventional formulations well known in the art,for example as described in standard textbooks of pharmaceutics such asthe British Pharmacopoeia.

The drug may also be formulated for inhalation, for example as a nasalspray, or dry powder or aerosol inhalers. For delivery by inhalation,the active compound is preferably in the form of microparticles. Theymay be prepared by a variety of techniques, including spray-drying,freeze-drying and micronisation. Aerosol generation can be carried outusing, for example, pressure-driven jet atomizers or ultrasonicatomizers, preferably using propellant-driven metered aerosols orpropellant-free administration of micronized active compounds from, forexample, inhalation capsules or other “dry powder” delivery systems.

The active ingredient may also be administered parenterally in a sterilemedium. Depending on the vehicle and concentration used, the drug caneither be suspended or dissolved in the vehicle. Advantageously,adjuvants such as a local anaesthetic, preservative and buffering agentscan be dissolved in the vehicle.

Other compounds may be combined with compounds of this invention for theprevention and treatment of prostaglandin-mediated diseases. Thus thepresent invention is also concerned with pharmaceutical compositions forpreventing and treating PGD₂-mediated diseases comprising atherapeutically effective amount of a compound of the invention and oneor more other therapeutic agents. Suitable therapeutic agents for acombination therapy with compounds of the invention include, but are notlimited to: (1) corticosteroids, such as fluticasone, budesonide orciclesonide; (2) β2-adrenoreceptor agonists, such as salmeterol,formeterol or indacaterol; (3) leukotriene modulators, for exampleleukotriene antagonists such as montelukast or pranlukast or leukotrienebiosynthesis inhibitors such as Zileuton or BAY-x1005; (4)anticholinergic agents, for example muscarinic-3 (M₃) receptorantagonists such as tiotropium bromide; (5) phosphodiesterase-IV(PDE-IV) inhibitors, such as roflumilast or cilomilast; (6)antihistamines, for example selective histamine-1 (H1) receptorantagonists, such as loratidine or astemizole; (7) antitussive agents,such as codeine or dextramorphan; (8) non-selective COX-1/COX-2inhibitors, such as ibuprofen or ketoprofen; (9) COX-2 inhibitors, suchas celecoxib and rofecoxib; (10) VLA-4 antagonists, such as thosedescribed in WO97/03094 and WO97/02289; (11) TNF-α inhibitors, forexample anti-TNF monoclonal antibodies, such as Remicade and CDP-870 andTNF receptor immunoglobulin molecules, such as Enbrel; (12) inhibitorsof matrix metalloprotease (MMP), for example MMP8, 9 and 12; (13) humanneutrophil elastase inhibitors, such as those described in WO2005/026124and WO2003/053930; (14) Adenosine A2a agonists such as those describedin EP1052264 and EP1241176 (15) Adenosine A2b antagonists such as thosedescribed in WO2002/42298; (16) modulators of chemokine receptorfunction, for example antagonists of CCR3 and CCR8; (17) compounds whichmodulate the action of other prostanoid receptors, for example a PGD2(DP) receptor antagonist or a thromboxane A2 antagonist; and (18)compounds which modulate Th2 function, for example, PPAR agonists.

The weight ratio of the compound of the invention to the second activeingredient may be varied and will depend upon the effective dose of eachingredient. Generally, an effective dose of each will be used.

Biological Methods

Compounds of the invention can be tested using the following biologicaltest methods to determine their ability to displace PGD₂ from the CRTH2receptor and for their ability to antagonise the functional effects ofPGD₂at the CRTH2 receptor in a whole cell system.

Radioligand Binding Assay

The receptor binding assay is performed in a final volume of 200 μLbinding buffer [10 mM BES (pH 7.4), 1 mM EDTA, 10 mM manganese chloride,0.01% BSA] and 1 nM [³H]-PGD₂ (Amersham Biosciences UK Ltd). Ligands areadded in assay buffer containing a constant amount of DMSO (1% byvolume). Total binding is determined using 1% by volume of DMSO in assaybuffer and non-specific binding is determined using 10 μM of unlabeledPGD₂ (Sigma). Human embryonic kidney (HEK) cell membranes (3.5 μg)expressing the CRTH2 receptor are incubated with 1.5 mg wheatgermagglutinin SPA beads and 1 nM [³H]-PGD₂ (Amersham Biosciences UK Ltd)and the mixture incubated for 3 hours at room temperature. Bound[³H]-PGD₂ is detected using a Microbeta TRILUX liquid scintillationcounter (Perkin Elmer). Compound IC₅₀ value is determined using a6-point dose response curve in duplicate with a semi-log compounddilution series. IC₅₀ calculations are performed using Excel and XLfit(Microsoft), and this value is used to determine a Ki value for the testcompound using the Cheng-Prusoff equation.

Functional Assay

Calcium Mobilisation (Flux) Assay

Stable CHO-K1 cells co-expressing the CRTH2 receptor and the G-proteinGα16 are seeded (40,000 cells per well in a plating volume of 75 μL inF-12 Hams supplemented with 1% foetal bovine serum) into collagen-coated96-well plates 24 hours prior to the assay. The cells are then loadedwith a fluorescence-imaging plate reader (FLIPR) calcium kit dye(Calcium 3 kit, Molecular Devices Ltd) containing 5 mM finalconcentration of probenecid and incubated at 37° C. for 1 hour in a 5 %CO₂ atmosphere. The fluorescence emission caused by intracellularcalcium mobilization elicited by the PGD₂ at the CRTH2 receptor isdetermined with a FLEXstation benchtop scanning and integrated fluidtransfer workstation (Molecular Devices Ltd). To detect antagonists anddetermine compound IC₅₀, compounds are pre-incubated at varyingconcentrations with the loaded cells for 15 minutes at 37° C., 5 % CO₂,prior to the addition of the agonist at its EC₈₀ value. Compounds andagonist are added in Hanks balanced salt solution containing 20 mM HEPESand 0.1% BSA). The fractional response values for each well arecalculated by subtracting the basal response from the peak response.Results are calculated as the mean of triplicate wells using Excel andXLfit (Microsoft).

The following examples describe the preparation of compounds of theinvention:

Examples

¹H NMR spectra were recorded at ambient temperature using a Varian UnityInova (400 MHz) spectrometer with a triple resonance 5 mm probespectrometer. Chemical shifts are expressed in ppm relative totetramethylsilane. The following abbreviations have been used: brs=broad singlet, s=singlet, d=doublet, dd=double doublet, t=triplet,q=quartet, m=multiplet.

Mass Spectrometry (LCMS) experiments to determine retention times andassociated mass ions were performed using the following methods:

Method A: experiments were performed on a Micromass Platform LCTspectrometer with positive ion electrospray and single wavelength UV 254nm detection using a Higgins Clipeus C18 5 μm 100×3.0 mm column and a 2mL/minute flow rate. The initial solvent system was 95% water containing0.1% formic acid (solvent A) and 5% acetonitrile containing 0.1% formicacid (solvent B) for the first minute followed by a gradient up to 5%solvent A and 95% solvent B over the next 14 minutes. The final solventsystem was held constant for a further 2 minutes.

Method B: experiments were performed on a Micromass Platform LCspectrometer with positive and negative ion electrospray and ELS/Diodearray detection using a Phenomenex Luna C18(2) 30×4.6 mm column and a 2mL/minute flow rate. The solvent system was 95% solvent A and 5% solventB for the first 0.50 minutes followed by a gradient up to 5% solvent Aand 95% solvent B over the next 4 minutes. The final solvent system washeld constant for a further 0.50 minutes Microwave experiments werecarried out using a Personal Chemistry Smith Synthesizer™, which uses asingle-mode resonator and dynamic field tuning, both of which givereproducibility and control. Temperatures from 40-250° C. can beachieved, and pressures of up to 20 bar can be reached. Two types ofvial are available for this processor, 0.5-2.0 mL and 2.0-5.0 mL.

Reverse-phase preparative HPLC purifications were carried out usingGenesis 7 micron C-18 bonded silica stationary phase in columns 10 cm inlength and 2 cm Internal diameter. The mobile phase used was mixtures ofacetonitrile and water (both buffered with 0.1% v/v trifluoroaceticacid) with a flow rate of 10 mL per minute and typical gradients of 40to 90% organic modifier ramped up over 30 to 40 minutes. Fractionscontaining the required product (identified by LC-MS analysis) werepooled, the organic fraction removed by evaporation, and the remainingaqueous fraction lyophilised, to give the final product.

Example 1[3-(2,4dichlorophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid

Preparation 1a: 3-(5-fluoropyridin-2-yl)propionic acid ethyl ester

A solution of 3-ethoxy-3-oxopropylzinc bromide in tetrahydrofuran (0.5M, 630 mL) was added dropwise to a mixture of 2-bromo-5-fluoropyridine(50 g), tetrakis(triphenylphosphine)palladium(0), (5.5 g) and toluene(350 mL) at room temperature. The resulting mixture was stirred at roomtemperature for 24 hours and then concentrated under reduced pressure.The residue was diluted with ethyl acetate, filtered through hyflo andthe filtrate washed with saturated aqueous sodium chloride solution anddried over magnesium sulfate. The solvent was removed under reducedpressure and the residue purified by column chromatography on silicagel, eluting with a mixture of pentane and ethyl acetate (9:1 by volume)to afford title compound as a yellow oil, 35 g.

¹H NMR (CDCl₃): δ 1.25 (t, J=7.1 Hz, 3H), 2.75 (t, J=7.4 Hz, 2H), 3.10(t, J=7.4 Hz, 2H), 4.10 (q, J=7.1 Hz, 2H), 7.20 (dd, J=4.4, 8.4 Hz, 1H),7.30 (dt, J=3.0, 8.4 Hz, 1H), 8.35 (d, J=2.6 Hz, 1H).

Preparation 1b: (6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester

A mixture of 3-(5-fluoropyridin-2-yl)propionic acid ethyl ester (12 g)and acetonitrile (90 mL) at room temperature was treated with a solutionof 1-bromopropan-2-one (16 g) in acetonitrile (30 mL) and the resultingmixture heated at reflux for 24 hours and then left to stand at roomtemperature for 60 hours. The mixture was treated with pyridine (35 mL)and the resulting mixture was heated at reflux for four hours, cooled toroom temperature and then concentrated under reduced pressure. Theresidue was diluted with ethyl acetate, washed with water and saturatedaqueous sodium hydrogen chloride solution and dried over magnesiumsulfate. The solvent was removed under reduced pressure and the residuepurified by column chromatography on silica gel, eluting with a mixtureof pentane and ethyl acetate (19:1 by volume) to afford title compoundas a yellow oil, 3.7 g.

¹H NMR (CDCl₃): δ 1.25 (t, J=7.1 Hz, 3H), 2.25 (s, 3H), 3.65 (s, 2H),4.11 (q, J=7.1 Hz, 2H), 6.55 (m, 1H), 7.10 (br s, 1H), 7.25 (m, 1H),7.70 (d, J=3.4 Hz, 1H).

Preparation 1c:[3-(2,4-dichlorophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester

A mixture of (6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester(0.10 g) and toluene (20 mL) was treated with2,4-dichlorobenzenesulfonyl chloride (0.16 g) and aluminium chloride(0.010 g) and the resulting mixture was heated at reflux for 24 hours.The mixture was cooled to room temperature, concentrated under reducedpressure and the residue diluted with a mixture of ethyl acetate andwater. The mixture was filtered through hyflo and the organic filtratedried over magnesium sulfate. The solvent was removed under reducedpressure and the residue purified by column chromatography on silicagel, eluting with a mixture of pentane and ethyl acetate (19:1 byvolume) to afford title compound as a light brown oil, 0.052 g.

¹H NMR (CDCl₃): δ 1.25 (t, J=7.1 Hz, 3H), 2.35 (s, 3H), 3.75 (s, 2H),4.15 (q, J=7.1 Hz, 2H) 6.00 (d, J=8.5 Hz,₁ H), 6.80 (m, 1H), 6.90 (d,J=2.1 Hz, 1H), 7.35 (d, J=2.1 Hz, 1H), 7.40 (dd, J=5.2, 9.7 Hz, 1H),8.00 (dd, J=2.1, 5.2 Hz, 1H)

Preparation 1d:[3-(2,4-dichlorophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid

A mixture of[3-(2,4-dichlorophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester (0.052 g) and methanol (2.0 mL) was treated with 1.0 Maqueous lithium hydroxide solution and the resulting mixture was stirredat room temperature for 2 hours. The mixture was concentrated underreduced pressure, diluted with water and acidified by the addition of1.0 M aqueous hydrochloric acid. The mixture was extracted withdichloromethane and the combined extracts dried over magnesium sulfateand the solvent removed under reduced pressure. The residue was purifiedby preparative reverse-phase HPLC using a gradient over 30 minutes ofacetonitrile in water (70% to 95% of organic modifier) to afford titlecompound as a white solid, 0.032 g.

¹H NMR (CDCl₃): δ 2.35 (s, 3H), 3.80 (s, 2H), 6.00 (d, J=8.5 Hz, 1H),6.80 (m, 1H), 6.90 (dd, J=2.1, 8.5 Hz, 1H), 7.35 (d, J=1.9 Hz, 1H), 7.40(m, 1H), 8.00 (dd, J=1.9, 5.0 Hz, 1H).

MS: ESI (+ve) (Method A): 384 (M+H)⁺, Retention time 14.0 min.

Example 2[6-fluoro-3-(2-fluoro-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

Preparation 2a: 1,2-difluoro-4-methanesulfonylbenzene

3-Chlordperoxybenzoic acid (19 g) was added portionwise to a solution of1,2-difluoro-4-methylsulfanylbenzene (5.4 g) in dichloromethane (100 mL)at room temperature and the resulting mixture was stirred at roomtemperature overnight. The mixture was washed with saturated aqueoussodium thiosulfate solution and saturated aqueous sodium hydrogencarbonate solution and then dried over magnesium sulfate. The solventwas removed under reduced pressure to afford title compound as a whitesolid, 5.5 g.

¹H NMR (CDCl₃): δ 3.05 (s, 3H), 7.40 (m, 1H), 7.75-7.85 (m, 2H).

Preparation 2b: bis(2-fluoro-4-methanesulfonylbenzene)disulfide

A mixture of 1,2-difluoro-4-methanesulfonylbenzene (2.8 g), sodiumhydrogensulfide (11 g) and 1-methylpyrrolidin-2-one (30 mL) was stirredat 80° C. for 90 minutes and then at room temperature overnight. Themixture was diluted with water (40 mL), acidified by the addition ofconcentrated hydrochloric acid and then extracted with ethyl acetate.The combined extracts were dried over magnesium sulfate and the solventremoved under reduced pressure. The residue was crystallised fromtoluene to afford title compound as cream crystals, 1.4 g.

MS: ESI (+ve) (Method B): 411 (M+H)⁺, Retention time 3.1 min.

Preparation 2c:[6-fluoro-3-(2-fluoro-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid ethyl ester

Sulfuryl chloride (0.066 mL) was added to a mixture ofbis(2-fluoro-4-methanesulfonylbenzene)disulfide (0.39 g) anddichloroethane (5.0 mL) at 0° C. and the resulting mixture was stirredat room temperature for 30 minutes. A solution of(6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester (0.15 g) indichloroethane (5.0 mL) was added and the resulting mixture stirred atroom temperature overnight. The mixture was concentrated under reducedpressure and the residue purified by column chromatography on silicagel, eluting with mixture of toluene, dichloromethane and ethyl acetate(1:4:0 to 0:1:0 to 0:9:1 by volume) to afford title compound as a yellowsolid, 0.25 g.

MS: ESI (+ve) (Method B): 440 (M+H)⁺, Retention time 4.1 min.

Preparation 2d:6-fluoro-3-(2-fluoro-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

A mixture of[6-fluoro-3-(2-fluoro-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid ethyl ester (0.25 g), tetrahydrofuran (3.0 mL) and 1.0 M aqueouslithium hydroxide solution (3.0 mL) was stirred at room temperature for3 hours. The tetrahydrofuran was removed under reduced pressure and thepH of the residue adjusted to 4 by the addition of sodiumdihydrogenphosphate. The resulting precipitate was collected byfiltration to afford title compound, 0.22 g.

¹H NMR (DMSO-d6): 2.25 (s, 3H), 3.20 (s, 3H), 3.70 (s, 2H), 6.40 (dd,J=7.5, 8.1 Hz, 1H), 7.00 (m, 1H), 7.55 (dd, J=1.8, 8.3 Hz, 1H), 7.70(dd, J=5.5, 9.8 Hz, 1H), 7.85 (dd, J=1.8, 7.5 Hz, 1H), 8.35 (dd, J=2.1,5.5 Hz, 1H).

MS: ESI (+ve) (Method A): 412 (M+H)⁺, Retention time 10.2 min.

Example 3[6-fluoro-3-(4-methanesulfonyl-2-trifluoromethylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

Preparation 3a: 1-fluoro-4-methylsulfanyl-2-trifluoromethylbenzene

A mixture of dimethyl disulfide (2.0 mL),4-fluoro-3-trifluoromethylphenylamine (2.0 g) and acetonitrile (50 mL)at room temperature was treated dropwise with isopentyl nitrite (2.0 mL)and the resulting mixture was stirred at 60° C. for 16 hours. Themixture was cooled to room temperature, diluted with water and extractedwith ethyl acetate. The combined extracts were dried over magnesiumsulfate and the solvent was removed under reduced pressure to affordtitle compound, 0.67 g.

¹H NMR (CDCl₃): δ 2.50 (s, 3H), 7.15 (m, 1H), 7.40-7.50 (m, 2H).

Preparation 3b: 1-fluoro-4-methanesulfonyl-2-trifluoromethylbenzene

3-Chloroperoxybenzoic acid (2.4 g) was added portionwise to a solutionof 1-fluoro-4-methylsulfanyl-2-trifluoromethylbenzene (1.3 g) indichloromethane (50 mL) at room temperature and the resulting mixturewas stirred at room temperature for 3 hours. The mixture was filteredand the filtrated washed with saturated aqueous sodium thiosulfatesolution and saturated aqueous sodium chloride solution and then driedover magnesium sulfate. The solvent was removed under reduced pressureto afford title compound, 1.5 g.

¹H NMR (CDCl₃): δ 3.1 (s, 3H), 7.45 (t, J=9.3 Hz, 1H), 8.20 (m, 1H),8.25 (m, 1H).

Preparation 3c: bis(2-trifluoromethyl-4-methanesulfonylbenzene)disulfide

A mixture of 1-fluoro-4-methanesulfonyl-2-trifluoromethylbenzene (1.4g), sodium hydrogensulfide (4.6 g) and 1-methylpyrrolidin-2-one (6.0 mL)was stirred at 80° C. for 2 hours and then at room temperatureovernight. The mixture was diluted with water, washed with ethyl acetateand the aqueous phase acidified by the addition of concentratedhydrochloric acid. The mixture was extracted with ethyl acetate and thecombined extracts dried over magnesium sulfate and the solvent removedunder reduced pressure. The residue was triturated with ethyl acetate toafford title compound, 0.94 g.

Preparation 3d:[6-fluoro-3-(2-trifluoromethyl-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid ethyl ester

Sulfuryl chloride (0.060 mL) was added to a mixture ofbis(2-trifluoromethyl-4-methanesulfonylbenzene)disulfide (0.45 g) anddichloroethane (10 mL) at 0° C. and the resulting mixture was stirred atroom temperature for 30 minutes and then at 60° C. for 4 hours. Asolution of (6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester(0.15 g) in dichloroethane (5.0 mL) was added and the resulting mixturestirred 60° C. overnight. The mixture was concentrated under reducedpressure and the residue purified by column chromatography on silicagel, eluting with mixture of cyclohexane, dichloromethane and ethylacetate (1:4:0 to 0:19:1 by volume). Further purification by preparativereverse-phase HPLC using a gradient over 20 minutes of acetonitrile. inwater (50% to 98% of organic modifier) gave title compound as a yellowsolid, 0.030 g.

MS: ESI (+ve) (Method B): 490 (M+H)⁺, Retention time 4.3 min.

Preparation 3e:[6-fluoro-3-(4-methanesulfonyl-2-trifluoromethylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

The title compound was prepared by the method of Preparation 2d using[6-fluoro-3-(2-fluoro-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid ethyl ester

¹H NMR (DMSO-d6): δ 2.25 (s, 3H), 3.25 (s, 3H), 3.80 (s, 2H), 6.50 (d,J=8.5 Hz, 1H), 7.10 (m, 1H), 7.70 (dd, J=5.5, 9.8 Hz, 1H), 7.90 (dd,J=1.9, 8.4 Hz, 1H), 8.20 (d, J=1.9 Hz, 1H), 8.20 (m, 1H), 12.20 (br s,1H).

MS: ESI (+ve) (Method A): 462 (M+H)⁺, Retention time 11.1 min.

Example 4(R)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid

Preparation 4a: (R)-3-(5-fluoropyridin-2-yl)-2-methylpropionic acidmethyl ester

A solution of (S)-3-methoxy-2-methyl-3-oxopropylzinc bromide intetrahydrofuran (0.5 M, 20 mL) was added dropwise to a mixture of2-bromo-5-fluoropyridine (1.0 g),tetrakis(triphenylphosphine)palladium(0), (0.14 g) and toluene (20 mL)at room temperature. The resulting mixture was stirred at roomtemperature for 6 hours and then left to stand at room temperatureovernight. The mixture was concentrated under reduced pressure and theresidue diluted with a mixture of ethyl acetate and water. The mixturewas filtered through hyflo and the organic filtrate washed with waterand saturated aqueous sodium chloride solution and then dried overmagnesium sulfate. The solvent was removed under reduced pressure andthe residue purified by column chromatography on silica gel, elutingwith a mixture of pentane and ethyl acetate (9:1 by volume) to affordtitle compound, 0.87 g.

¹H NMR (CDCl₃): δ 1.20 (d, J=7.0 Hz, 3H), 2.85 (dd, J=6.6, 13.7 Hz, 1H),3.00 (m, 1H), 3.20 (dd, J=7.6, 13.7 Hz, 1H), 3.65 (s, 3H), 7.15 (dd,J=4.4, 8.5 Hz, 1H), 7.30 (dt, J=2.9, 8.5 Hz, 1H), 8.40 (d, J=2.9 Hz,1H).

Preparation 4b: (R)-2-(6-fluoro-2-methylindolizin-1-yl)propionic acidmethyl ester

The title compound was prepared by the method of Preparation 1b using(R)-3-(5-fluoropyridin-2-yl)-2-methylpropionic acid methyl ester.

MS: ESI (+ve) (Method B): 236 (M+H)⁺, Retention time 3.7 min.

Preparation 4c: bis[4-(methylsulfonyl)phenyl]disulfide

A mixture of 1-fluoro-4-methanesulfonylbenzene (32 g), sodiumhydrogensulfide (64 g) and 1-methylpyrrolidin-2-one (100 mL) was stirredat 80° C. for 60 minutes and then at room temperature for 60 minutes.The mixture was diluted with water, filtered and the filtrate acidifiedby the addition of concentrated hydrochloric acid. The resultingprecipitate was collected by filtration, washed with water and dried toafford title compound as a white solid, 15 g.

MS: ESI (+ve) (Method B): 375 (M+H)⁺, Retention time 3.3 min.

Preparation 4d:(R)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid methyl ester

The title compound was prepared by the method of Preparation 2c using(R)-3-(5-fluoropyridin-2-yl)-2-methylpropionic acid methyl ester andbis[4-(methylsulfonyl)phenyl]disulfide.

MS: ESI (+ve) (Method B): 422 (M+H)⁺, Retention time 4.0 min.

Preparation 4e:(R)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid

The title compound was prepared by the method of Preparation 1d using(R)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid methyl ester

¹H NMR (CDCl₃): δ 1.60 (d, J=7.1 Hz, 3H), 2.35 (s, 3H), 3.00 (s, 3H),4.10 (q, J=7.1 Hz, 1H), 6.80 (m, 1H), 6.90 (d, J=8.6 Hz, 2H), 7.50 (dd,J=5.3, 9.7 Hz, 1H), 7.70 (d, J=8.6 Hz, 2H), 8.00 (m, 1H).

MS: ESI (+ve) (Method A): 408 (M+H)⁺, Retention time 10.4 min.

Example 5[3-(4-ethanesulfonylphenylsulfanyl)+fluoro-2-methylindolizin-1-yl]aceticacid

Preparation 5a: 1-ethylsulfanyl-4-fluorobenzene

A mixture of diethyl disulfide (11 mL), 4-fluorophenylamine (5.0 g) anddichloromethane (50 mL) at room temperature was treated dropwise withtert-butyl nitrite (7.7 mL) and the resulting mixture stirred at 50° C.for 5 minutes and then at room temperature for 3 hours. The mixture waswashed with water and 1.0 M aqueous hydrochloric acid and then driedover magnesium sulfate. The solvent was removed under reduced pressureand the residue purified by column chromatography on silica gel, elutingwith cyclohexane to afford title compound, 3.5

¹H NMR (CDCl₃): δ 1.25 (t, J=7.3 Hz, 3H), 2.90 (q, J=7.3 Hz, 2H), 7.00(m, 2H), 7.35 (m, 2H).

Preparation 5b: 1-ethanesulfonyl-4-fluorobenzene

A solution of 1-ethylsulfanyl-4-fluorobenzene (3.5 g) in dichloromethane(20 mL) at room temperature was treated with 3-chloroperoxybenzoic acid(6.0 g) and the resulting mixture was stirred at room temperatureovernight. The mixture was washed with saturated aqueous sodium hydrogencarbonate solution, dried over magnesium sulfate and the solvent removedunder reduced pressure to afford title compound, 4.3 g.

¹H NMR (DMSO-d6): δ 1.10 (t, J=7.3 Hz, 3H), 3.30 (q, J=7.3 Hz, 2H), 7.50(m, 2H), 8.00 (m, 2H).

Preparation 5c: bis(4-ethanesultonylbenzene)disulfide

A mixture of 1-ethanesulfonyl-4-fluorobenzene (1.0 g), sodiumhydrogensulfide (4.4 g) and 1-methylpyrrolidin-2-one (4.0 mL) wasstirred at 80° C. for 2 hours and then at room temperature overnight.The mixture was diluted with water, washed with ethyl acetate and theaqueous phase acidified by the addition of 1.0 M aqueous hydrochloricacid. The mixture was extracted with ethyl acetate and the combinedextracts dried over magnesium sulfate and the solvent removed underreduced pressure to afford title compound, 0.80 g.

¹H NMR (DMSO-d6): δ 1.10 (t, J=7.4 Hz, 6H), 3.30 (q, J=7.4 Hz, 4H),7.80-7.90 (m, 8H).

Preparation 5d:[3-(4-ethanesulfonylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester

The title compound was prepared by the method of Preparation 2c using(6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester andbis(4-ethanesulfonylbenzene)disulfide.

MS: ESI (+ve) (Method B): 436 (M+H)⁺, Retention time 4.1 min.

Preparation 5e:[3-(4-ethanesulfonylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid

A solution of[3-(4-ethanesulfonylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester (0.14 g) in tetrahydrofuran (6.0 mL) was treated with asolution of lithium hydroxide (0.040 g) in water (6.0 mL) and theresulting mixture was stirred at room temperature for 1 hour. Themixture was acidified by the addition of 1.0 M aqueous hydrochloricacid, extracted with ethyl acetate and the combined extractsconcentrated under reduce pressure. The residue was purified bypreparative reverse-phase HPLC using a gradient of acetonitrile in waterto afford title compound as a green solid, 0.020 g.

¹H NMR (CD₃OD): δ 1.15 (t, J=7.5 Hz, 3H), 2.30(s, 3H), 3.10 (q, J=7.5Hz, 2H), 3.75 (s, 2H), 6.85 (m, 1H), 7.00 (d, J=8.7 Hz, 2H), 7.55 (m,1H), 7.70 (d, J=8,7 Hz, 2H), 8.10 (dd, J=2.1, 5.4 Hz, 1H).

MS: ESI (+ve) (Method A): 435 (M+H)⁺, Retention time 10.2 min.

Example 6(S)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid

Preparation 6a: (S)-3-(5-fluoropyridin-2-yl)-2-methylpropionic acidmethyl ester

The title compound was prepared by the method of Preparation 4a using(R)-3-methoxy-2-methyl-3-oxopropylzinc bromide and2-bromo-5-fluoropyridine.

MS: ESI (+ve) (Method B): 198 (M+H)⁺, Retention time 2.6 min.

Preparation 6b: (S)-2-(6-fluoro-2-methylindolizin-1-yl)propionic acidmethyl ester

The title compound was prepared by the method of Preparation 1b using(S)-3-(5-fluoropyridin-2-yl)-2-methylpropionic acid methyl ester.

MS: ESI (+ve) (Method B): 236 (M+H)⁺, Retention time 3.7 min.

Preparation 6c:(S)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid methyl ester

The title compound was prepared by the method of Preparation 2c using(S)-2-(6-fluoro-2-methylindolizin-1-yl)propionic acid methyl ester andbis[4-(methylsulfonyl)phenyl]disulfide.

MS: ESI (+ve) (Method B): 422 (M+H)⁺, Retention time 4.0 min.

Preparation 6d:(S)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid methyl ester

A mixture of(S)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid methyl ester (0.25 g), methanol (10 mL) and 1.0 M aqueous lithiumhydroxide solution (3.0 mL) was stirred at 65° C. for 8 hours. Themixture was concentrated under reduced pressure, diluted with water andwashed with dichloromethane. The aqueous phase was acidified by theaddition of glacial acetic acid, extracted with dichloromethane and thecombined extracts dried over magnesium sulfate. The solvent was removedunder reduced pressure and the residue purified by preparativereverse-phase HPLC using a gradient over 30 minutes of acetonitrile inwater (50% to 98% of organic modifier) to afford title compound as apale green solid, 0.17 g.

¹H NMR (CDCl₃): δ 1.60 (d, J=7.4 Hz, 3H), 2.35 (s, 3H), 3.00 (s, 3H),4.05 (q, J=7.4 Hz, 1H), 6.75 (m, 1H), 6.90 (d, J=8.6 Hz, 2H), 7.50 (dd,J=5.3, 9.7 Hz, 1H), 7.70 (d, J=8.6 Hz, 2H), 8.80 (dd, J=2.0, 4.5 Hz,1H).

MS: ESI (+ve) (Method A): 408 (M+H)⁺, Retention time 10.6 min.

Example 7ethanesulfonylaminobenzenesulfonyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid

Preparation 7a: ethanesulfonic acid[4-(4-ethanesulfonylaminophenyldisulfanyl)phenyl]amide

A solution of ethanesulfonyl chloride (1.9 mL) in dichloromethane (5.0mL) was added dropwise to a solution of 4-aminophenyl disulfide (2.0 g)and triethylamine (4.5 mL) in dichloromethane (20 mL) at −40° C. and theresulting mixture was warmed to room temperature over a period of 4hours. The mixture was washed with 1.0 M aqueous sodium hydroxidesolution and the aqueous phase acidified by the addition of 1.0 Maqueous hydrochloric acid and then extracted with ethyl acetate. Thecombined extracts were dried over magnesium sulfate and solvent removedunder reduced pressure to afford title compound as a white solid, 2.0 g.

¹H NMR (DMSO-d6): δ 1.15 (t, J=7.4 Hz, 6H), 3.10 (q, J=7.4 Hz, 4H), 7.20(m, 4H), 7.45 (m, 4H), 9.85 (br s, 2H).

Preparation 7b:[3-(4-ethanesulfonylaminophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester

The title compound was prepared by the method of Preparation 2c using(6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester andethanesulfonic acid[4-(4-ethanesulfonylaminophenyldisulfanyl)phenyl]amide.

¹H NMR (CDCl₃): δ 1.25 (t, J=7.2 Hz, 3H), 1.35 (t, J=7.2 Hz, 3H), 2.35(s, 3H), 3.05 (q, J=7.2 Hz, 2H), 3.75 (s, 2H), 4.15 (q, J=7.2 Hz, 2H),6.25 (s, 1H), 6.75 (m, 1H), 6.80 (d, J=8.7 Hz, 2H), 7.05 (d, J=8.7 Hz,2H), 7.40 (dd, J=5.1, 9.8 Hz, 1H), 8.1 (dd, J=2.1, 5.1 Hz, 1H).

Preparation 7c:[3-(4-ethanesulfonylaminobenzenesulfonyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid methyl ester

A mixture of[3-(4-ethanesulfonylaminophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester (0.030 g), 3-chloroperoxybenzoic acid (0.090 g),potassium carbonate (0.092 g) and methanol was stirred at roomtemperature for 3 hours. The mixture was concentrated under reducedpressure, diluted with water and extracted with dichloromethane. Thecombined extracts were washed with saturated aqueous sodium chloridesolution, dried over magnesium sulfate and the solvent removed underreduced pressure to afford title compound.

MS: ESI (+ve) (Method B): 469 (M+H)⁺, Retention time 3.3 min.

Preparation 7d:ethanesulfonylaminobenzenesulfonyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid

The title compound was prepared by the method of Preparation 1d using[3-(4-ethanesulfonylaminobenzenesulfonyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester.

MS: ESI (+ve) (Method A): 455 (M+H)⁺, Retention time 9.1 min.

MS: ESI (+ve) (Method B): 455 (M+H)⁺, Retention time 3.1 min.

Example 8[7-chloro-6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

Preparation 8a:[7-chloro-6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid ethyl ester

Sulfuryl chloride (0.40 mL) was added to a mixture ofbis[4-(methylsulfonyl)phenyl]disulfide (1.6 g) and dichloromethane (40mL) at 0° C. and the resulting mixture was stirred at 0° C. for 10minutes and then at room temperature for 90 minutes. A solution of(6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester (1.0 g) indichloroethane (5.0 mL) was added and the resulting mixture stirred atroom temperature overnight. The mixture was diluted with dichloromethaneand saturated aqueous sodium hydrogen carbonate solution and the organicphase was washed with water and saturated aqueous sodium chloridesolution and then dried over magnesium sulfate. The solvent was removedunder reduced pressure and the residue purified by column chromatographyon silica gel, eluting with a mixture of cyclohexane and ethyl acetate(9:1 to 85:15 by volume) to afford title compound.

MS: ESI (+ve) (Method B): 456 (M+H)⁺, Retention time 4.3 min.

Preparation 8b:[7-chloro-6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

The title compound was prepared by the method of Preparation 1d using(7-chloro-6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid ethyl ester.

¹H NMR (CDCl₃): δ 2.30 (s, 3H), 3.00 (s, 3H), 3.75 (s, 2H), 6.90 (d,J=8.6 Hz, 2H), 7.45 (d, J=7.0 Hz, 1H), 7.70 (d, J=8.6 Hz, 2H), 8.05 (d,J=4.8 Hz, 1H).

MS: ESI (+ve) (Method A): 428 (M+H)⁺, Retention time 11.8 min.

MS: ESI (+ve) (Method B): 428 (M+H)⁺, Retention time 3.6 min.

Example 9[3-(2-chloro-4-methanesulfonylphenylsulfanyl)-7-cyano-2-methylindolizin-1-yl]aceticacid

Preparation 9a: 2-chloro-1-fluoro-4-methanesulfonylbenzene

A solution of sodium nitrite (5.7 g) in water (15 mL) was added dropwiseover a period 15 minutes to a mixture of2-fluoro-5-methanesulfonylphenylamine (15 g), concentrated hydrochloricacid (30 mL) and water (90 mL) at 0-10° C. The solution was added to amixture of copper chloride(l) (11.8 g) and concentrated hydrochloricacid (30 mL) at 0° C. and the resulting mixture heated at 40° C. for 10minutes. The mixture was cooled to room temperature, filtered and thefiltrate extracted with dichloromethane. The combined extracts weredried over magnesium sulfate and the solvent removed under reducedpressure. Purification of the residue by column chromatography on silicagel, eluting with a mixture of toluene, dichloromethane and ethylacetate (2:1:0 to 0:1:0 to 0:50:1 by volume) gave title compound as awhite solid, 3.7 g.

¹H NMR (CDCl₃): δ 3.05 (s, 3H), 7.35 (t, J=8.4 Hz, 1H), 7.85 (m, 1H),8.05 (dd, J=2.2, 6.6 Hz, 1H).

Preparation 9b: bis(2-chloro-4-methanesulfonylbenzene)disulfide

A mixture of 2-chloro-1-fluoro-4-methanesulfonylbenzene (1.0 g), sodiumhydrogensulfide (3.6 g) and 1-methylpyrrolidin-2-one (5.0 mL) wasstirred at 80° C. for 90 minutes and then at room temperature for 4hours. The mixture was diluted with water (40 mL) and acidified by theaddition of concentrated hydrochloric acid. The resulting precipitatewas collected by filtration, washed with water and ethanol and thencrystallised from toluene to give title compound as a white solid, 0.61g.

¹H NMR (DMSO-d6): δ 3.30 (s, 6H), 7.80 (d, J=8.3 Hz, 2H), 7.90 (dd,J=1.5, 8.3 Hz, 2H), 8.10 (br s, 2H).

MS: ESI (+ve) (Method B): 443 (M+H)⁺, Retention time 3.8 min.

Preparation 9c:[3-(2-chloro-4-methanesulfonylphenylsulfanyl)-7-cyano-2-methylindolizin-1-yl]aceticacid ethyl ester

The title compound was prepared by the method of Preparation 2c using(7-cyano-2-methylindolizin-1-yl)acetic acid ethyl ester andbis(2-chloro-4-methanesulfonylbenzene)disulfide.

MS: ESI (+ve) (Method B): 463 (M+H)⁺, Retention time 3.7 min.

Preparation 9d:[3-(2-chloro-4-methanesulfonylphenylsulfanyl)-7-cyano-2-methylindolizin-1-yl]aceticacid

A mixture of[3-(2-chloro-4-methanesulfonylphenylsulfanyl)-7-cyano-2-methylindolizin-1-yl]aceticacid ethyl ester (0.027 g), 5.0 M aqueous lithium hydroxide solution(0.25 mL), water (0.5 mL) and ethanol (5.0 mL) was stirred at roomtemperature for 1 hour. The mixture was acidified by the addition ofglacial acetic acid, concentrated under reduced pressure and the residuepartition between water (5.0 mL) and ethyl acetate (10 mL). The organicphase was dried over magnesium sulfate, concentrated under reducedpressure and the residue purified by preparative reverse-phase HPLCusing a gradient over 30 minutes of acetonitrile in water (45% to 95% oforganic modifier) to afford title compound, 0.019 g.

¹H NMR (DMSO-d6): δ 2.20 (s, 3H), 3.15 (s, 3H), 3.80 (s, 2H), 6.15 (d,J=8.6 Hz, 1H), 6.85 (dd, J=1.6, 7.1 Hz, 1H), 7.55 (dd, J =1.9, 8.4 Hz,1H), 8.00 (d, J=1.9 Hz, 1H), 8.20 (dd, J=0.9, 7.1 Hz, 1H), 8.35 (dd,J=0.9, 1.6 Hz, 1H).

MS: ESI (+ve) (Method A): 435 (M+H)⁺, Retention time 10.7 min.

Example 10[6-cyano-3-(4-methanesulfonylbenzyl)-2-methylindolizin-1-yl]acetic acid

Preparation 10a: 3-(5-cyanopyridin-2-yl)propionic acid ethyl ester

A solution of 3-ethoxy-3-oxopropylzinc bromide in tetrahydrofuran (0.5M, 60 mL) was added dropwise over a period of 45 minutes to a mixture of6-bromonicotinonitrile (5.0 g),tetrakis(triphenylphosphine)palladium(0), (0.69 g) and tetrahydrofuran(20 mL) at room temperature and the resulting mixture was stirred atroom temperature for 6 hours. The mixture was diluted with water (150mL), basified by the addition of saturated aqueous sodium hydrogencarbonate solution and extracted with methyl tert-butyl ether. Thecombined extracts were dried over magnesium sulfate and the solventremoved under reduced pressure. Purification of the residue by columnchromatography on silica gel, eluting with a mixture of pentane,dichloromethane and ethyl acetate (2:1:0, 0:1:0 and 0:5:1 by volume)gave title compound as a pale yellow oil, 4.1 9.

¹H NMR (CDCl₃): δ 1.25 (m, 3H), 2.85 (t, J=7.2 Hz, 2H), 3.2 (t, J=7.2Hz, 2H), 4.15 (m, 2H), 7.35 (d, J=8.0 Hz, 1H), 7.85 (m, 1H), 8.80 (s,1H).

MS: ESI (+ve) (Method B): 205 (M+H)⁺, Retention time 2.7 min.

Preparation 10b: (6-cyano-2-methylindolizin-1-yl)acetic acid ethyl ester

A mixture of 3-(5-cyanopyridin-2-yl)propionic acid ethyl ester (3.2 g),1-bromopropan-2-one (5.3 g mL), sodium hydrogen carbonate (3.9 g) andacetonitrile (40 mL) was heated at reflux for 41 hours. The mixture wascooled to room temperature, diluted with water and extracted with ethylacetate. The combined extracts were dried over magnesium sulfate and thesolvent removed under reduced pressure. Purification of the residue bycolumn chromatography on silica gel, eluting with a mixture ofdichloromethane and pentane (1:4 to 1:1 by volume) gave title compoundas a yellow solid, 0.51 g.

¹H NMR (CDCl₃): δ 1.25 (t, J=7.1 Hz, 3H), 2.30 (s, 3H), 3.65 (s, 2H),4.10 (q, J=7.1 Hz, 2H), 6.65 (dd, J=1.4, 9.3 Hz, 1H), 7.20 (m, 1H), 7.35(dd, J=0.9, 9.3 Hz, 1H), 8.20 (m, 1H).

MS: ESI (+ve) (Method B): 443 (M+H)⁺, Retention time 3.5 min.

Preparation 10c:[6-cyano-3-(4-methanesulfonylbenzyl)-2-methylindolizin-1-yl]acetic acidethyl ester

A mixture of (6-cyano-2-methylindolizin-1-yl)acetic acid ethyl ester(0.50 g), 4-methanesulfonylbenzaldehyde (0.38 g) and 1,2-dichloroethane(10 mL) at 0° C. was treated dropwise with triethylsilane (1.6 mL)followed by trifluoroacetic acid (0.46 mL) and the resulting mixture wasstirred at 0° C. for 10 minutes and then at room temperature overnight.The mixture was diluted with 1,2-dichloroethane (10 mL), washed withsaturated aqueous sodium hydrogen carbonate solution and dried overmagnesium sulfate. The solvent was removed under reduced pressure andthe residue purified by column chromatography on silica gel, elutingwith a mixture of cyclohexane and ethyl acetate (1:0 to 0:1 by volume)to afford title compound as a biege solid, 0.43 g.

MS: ESI (+ve) (Method B): 411 (M+H)⁺, Retention time 3.3 min.

Preparation 10d:[6-cyano-3-(4-methanesulfonylbenzyl)-2-methylindolizin-1-yl]acetic acid

The title compound was prepared by the method of Preparation 1d using[6-cyano-3-(4-methanesulfonylbenzyl)-2-methylindolizin-1-yl]acetic acidethyl ester.

¹H NMR (DMSO-d6): δ 2.30 (s, 3H), 3.00 (s, 3H), 3.75 (s, 2H), 4.30 (s,2H), 6.70 (dd, J=1.0, 9.3 Hz, 1H), 7.15 (d, J=8.5 Hz, 2H), 7.35 (dd,J=1.0, 9.3 Hz, 1H), 7.85 (m, 3H).

MS: ESI (+ve) (Method A): 383 (M+H)⁺, Retention time 8.8 min.

Example 11 [3-(4-chlorobenzyl)-7-cyano-2-methylindolizin-1-yl]aceticacid

Preparation 11a: 3-(4-cyanopyridin-2-yl)propionic acid ethyl ester

A solution of 3-ethoxy-3-oxopropylzinc bromide in tetrahydrofuran (0.5M, 8.0 mL) was added dropwise to a mixture of 2-chloroisonicotinonitrile(0.50 g), tetrakis(triphenylphosphine)palladium(0) (0.21 g) and toluene(8.0 mL) at room temperature and the resulting mixture was stirred at100° C. for 18 hours. The mixture was cooled to room temperature,diluted with saturated aqueous sodium hydrogen carbonate solution andextracted with ethyl acetate. The combined extracts were dried oversodium sulfate and the solvent removed under reduced pressure.Purification of the residue by column chromatography on silica gel,eluting with a mixture of cyclohexane and ethyl acetate (9:1 by volume)gave title compound, 0.44 g.

MS: ESI (+ve) (Method B): 205 (M+H)⁺, Retention time 2.8 min.

Preparation 14b: (7-cyano-2-methylindolizin-1-yl)acetic acid ethyl ester

A mixture of 3-(4-cyanopyridin-2-yl)propionic acid ethyl ester (0.78 g),1-bromopropan-2-one (1.3 g), sodium hydrogen carbonate (0.96 g) andacetonitrile (6.0 mL) was sealed in a flask and heated at 110° C. for 18hours. The mixture was cooled to room temperature and the solventremoved under reduced pressure. Purification of the residue by columnchromatography on silica gel, eluting with a mixture of cyclohexane andethyl acetate (19:1 by volume) gave title compound, 0.29 g.

MS: ESI (+ve) (Method B): 243 (M+H)⁺, Retention time 3.6 min.

Preparation 11c:[3-(4-chlorobenzyl)-7-cyano-2-methylindolizin-1-yl]acetic acid ethylester

The title compound was prepared by the method of Preparation 10c using(7-cyano-2-methylindolizin-1-yl)acetic acid ethyl ester and4-chlorobenzaldehyde.

MS: ESI (+ve) (Method B): 367 (M+H)⁺, Retention time 4.3 min.

Preparation 11d:[3-(4-chlorobenzyl)-7-cyano-2-methylindolizin-1-yl]acetic acid

The title compound was prepared by the method of Preparation 1d using[3-(4-chlorobenzyl)-7-cyano-2-methylindolizin-1-yl]acetic acid ethylester

¹H NMR (CDCl₃): δ 2.30 (s, 3H), 3.00 (s, 3H), 3.75 (s, 2H), 4.30 (s,2H), 6.70 (dd, J=1.3, 9.3 Hz, 1H), 7.15 (d, J=8.5 Hz, 2H), 7.35 (dd,J=0.8, 9.3 Hz, 1H), 7.80 (m, 3H)

MS: ESI (+ve) (Method A): 339 (M+H)⁺, Retention time 11.2 min.

Example 12[6-cyano-3-(6-fluoroquinolin-2-ylmethyl)-2-methylindolizin-1-yl]aceticacid

Preparation 12a:[6-cyano-3-(6-fluoroquinolin-2-ylmethyl)-2-methylindolizin-1-yl]aceticacid ethyl ester

The title compound was prepared by the method of Preparation 10c using6-cyano-2-methylindolizin-1-yl)acetic acid ethyl ester and6-fluoroquinoline-2-carbaldehyde.

MS: ESI (+ve) (Method B): 402 (M+H)⁺, Retention time 4.0 min.

Preparation 12b:[6-cyano-3-(6-fluoroquinolin-2-ylmethyl)-2-methylindolizin-1-yl]aceticacid

The title compound was prepared by the method of Preparation 1d using[6-cyano-3-(6-fluoroquinolin-2-ylmethyl)-2-methylindolizin-1-yl]aceticacid ethyl ester

¹H NMR (DMSO-d6): δ 2.25 (s, 3H), 3.80 (s, 2H), 4.65 (s, 2H), 6.80 (dd,J=1.4, 9.3 Hz, 1H), 7.35 (d, J=8.5 Hz, 1H), 7.55 (dd, J=1.0, 9.3 Hz,1H), 7.65 (dt, J=3.1, 8.8 Hz, 1H), 7.75 (dd, J=2.9, 9.3 Hz, 1H), 7.95(dd, J=5.4, 9.3 Hz, 1H), 8.30 (d, J=8.5 Hz, 1H), 9.05 (t, J=1.0 Hz, 1H).

MS: ESI (+ve) (Method A): 374 (M+H)⁺, Retention time 10.0 min.

Example 13 and 14[6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]acetic acidand[7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

Preparation 13a and 14a:[6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]acetic acidethyl ester and[7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid ethyl ester

The title compound was prepared by the method of Preparation 2c using(6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester andbis(4-methoxyphenyl) disulfide.

MS: ESI (+ve) (Method B): Retention time 4.5 min.

Preparation 13b and 14b:[6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]acetic acidand[7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

A mixture of[6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]acetic acidethyl ester and[7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid ethyl ester (0.35 g) and methanol (8.0 mL) was treated with 1.0 Maqueous sodium hydroxide solution (2.5 mL) and the resulting mixture wasstirred at room temperature for 3 hours. The mixture was concentratedunder reduced pressure, diluted with water and acidified by the additionof glacial acetic acid. The mixture was extracted with dichloromethaneand the combined extracts were washed with water and dried overmagnesium sulfate. The solvent was removed under reduced pressure andthe residue purified by preparative reverse-phase HPLC using a gradientof acetonitrile in water (55% to 80% of organic modifier) to afford[6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]acetic acidas a pale green solid, 0.20 g and[7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid as a pale yellow solid, 0.006 g.

[6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]acetic acid

¹H NMR (CDCl₃): δ 2.35 (s, 3H), 3.70 (s, 3H), 3.75 (s, 2H), 6.70-6.75(m, 3H), 6.85 (d, J=8.9 Hz, 2H), 7.30 (dd, J=5.2, 9.7 Hz, 1H), 8.10 (m,1H).

MS: ESI (+ve) (Method A): 346 (M+H)⁺, Retention time 11.7 min.

[7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid

¹H NMR (CDCl₃): δ 2.35 (s, 3H), 3.70 (s, 3H), 3.75 (s, 2H), 6.70 (d,J=8.8 Hz, 2H), 6.85 (d, J=8.8 Hz, 2H), 7.40 (d, J=7.1 Hz, 1H), 8.15 (d,J=5.1 Hz, 1H).

MS: ESI (+ve) (Method A): 380 (M+H)⁺, Retention time 12.5 min.

Example 15[3-(4-bromophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]acetic acid

Preparation 15a:[3-(4-bromophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]acetic acidethyl ester

The title compound was prepared by the method of Preparation 2c using(6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester and4-bromobenzenethiol.

MS: ESI (+ve) (Method B): Retention time 4.9 min.

Preparation 15b:[3-(4-bromophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]acetic acid

The title compound was prepared by the method of Preparation 13b and 14busing [3-(4-bromophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester.

¹H NMR CDCl₃): δ 2.30 (s, 3H), 3.75 (s, 2H), 6.65 (d, J=8.6 Hz, 2H),6.75 (m, 1H), 7.25 (d, J=8.6 Hz, 2H), 7.35 (dd, J=5.3, 9.7 Hz, 1H), 8.00(m, 1H).

MS: ESI (+ve) (Method A): 395 (M+H)⁺, Retention time 12.9 min.

Example 16[3-(4-cyclopropylsulfamoylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid

Preparation 16a: 4,4′-dithiobisbenzenesulfonic acid, disodium salt

Prepared by the method of Smith et al. (J. Org. Chem., 1964, 29,1484-1488).

Preparation 16b: 4,4′-dithiobisbenzenesulfonyl chloride

A mixture of 4,4′-dithiobisbenzenesulfonic acid, disodium salt (6.2 g),phosphorus oxychloride (6.2 mL) and phosphorus pentachloride (3.1 g) washeated at reflux for 2 hours. The mixture was cooled to roomtemperature, diluted with dichloromethane and poured into ice. Theorganic phase was washed with saturated aqueous sodium hydrogencarbonate solution, dried over magnesium sulfate and the solvent removedunder reduced pressure. The residue was triturated with cyclohexane toafford title compound as a light brown solid, 3.5 g.

¹H NMR (CDCl₃): δ 7.70 (m, 4H), 8.00 (m, 4H).

Preparation 16c: bis[(cyclopropyl-4-sulfonyl)benzene]disulfide

A solution of 4,4′-dithiobisbenzenesulfonyl chloride (1.0 g) indichloromethane (20 mL) was added dropwise to a mixture ofcyclopropylamine (0.4 mL), triethylamine (1.6 mL) and dichloromethane(15 mL) at 0° C. and the resulting mixture was stirred at roomtemperature for 2 days. The mixture was concentrated under reducedpressure and the residue was purified by column chromatography on silicagel, eluting with a mixture of dichloromethane and methanol (1:0 to 99:1by volume) to afford title compound as a pale yellow solid, 1.1 g.

MS: ESI (+ve) (Method B): 457 (M+H)⁺, Retention time 3.7 min.

Preparation 16d:[3-(4-cyclopropylsulfamoylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester

The title compound was prepared by the method of Preparation 2c using(6-fluoro-2-methylindolizin-1-yl)acetic acid ethyl ester andbis[(cyclopropyl-4-sulfonyl)benzene]disulfide.

MS: ESI (+ve) (Method B): 463 (M+H)⁺, Retention time 4.1 min.

Preparation 16e:[3-(4-cyclopropylsulfamoylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid

The title compound was prepared by the method of Preparation 1d using[3-(4-cyclopropylsulfamoylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid ethyl ester.

¹H NMR (CDCl₃): δ 0.55 (m, 4H), 2.15 (m, 1H), 2.30 (s, 3H), 3.75 (s,2H), 4.95 (br s, 1H), 6.80 (m, 1H), 6.90 (d, J=8.6 Hz, 2H), 7.35 (dd,J=5.1, 9.7 Hz, 1H), 7.65 (d, J=8.6 Hz, 2H), 8.00 (dd, J=1.9, 5.1 Hz,1H).

MS: ESI (+ve) (Method A): 435 (M+H)⁺, Retention time 10.8 min.

Biological Results:

Compounds of the Examples above were, tested in the CRTH2 RadioligandBinding assay described above; the compounds had Ki values of less than100 nM in the binding assay. For example, compounds of Examples 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 16 had Ki values of 27, 0.2,0.9, 29, 0.8, 57, 47, 0.4, 2.9, 1.7, 26, 7.2, 44, 23 and 0.6 nM,respectively. The compounds also generally had IC₅₀ values in thecalcium flux functional assay of less than 100 nM. For example,compounds of Examples 2, 3, 5 and 16 had IC₅₀ values of 6.6, 11, 8.9 and22 nM, respectively.

1. A compound selected from the group consisting of:[3-(2,4-dichlorophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid,[6-fluoro-3-(2-fluoro-4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,[6-fluoro-3-(4-methanesulfonyl-2-trifluoromethylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,(R)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid,(S)-2-[6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]propionicacid,[3-(4-ethanesulfonylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid,ethanesulfonylaminobenzenesulfonyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid,[7-chloro-6-fluoro-3-(4-methanesulfonylphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,[3-(2-chloro-4-methanesulfonylphenylsulfanyl)-7-cyano-2-methylindolizin-1-yl]aceticacid, [6-cyano-3-(4-methanesulfonylbenzyl)-2-methylindolizin-1-yl]aceticacid, [3-(4-chlorobenzyl)-7-cyano-2-methylindolizin-1-yl]acetic acid,[6-cyano-3-(6-fluoroquinolin-2-ylmethyl)-2-methylindolizin-1-yl]aceticacid,[6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid,[7-chloro-6-fluoro-3-(4-methoxyphenylsulfanyl)-2-methylindolizin-1-yl]aceticacid, [3-(4-bromophenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid,[3-(4-cyclopropylsulfamoylphenylsulfanyl)-6-fluoro-2-methylindolizin-1-yl]aceticacid, and salts, N-oxides, hydrates and solvates thereof.
 2. (canceled)3. A pharmaceutical composition comprising a compound as claimed inclaim 1 and a pharmaceutically acceptable carrier. 4-5. (canceled)
 6. Amethod of treatment of asthma, chronic obstructive pulmonary disease,rhinitis, allergic airway syndrome, or allergic rhinobronchitis,comprising administering to a patient suffering such disease aneffective amount of a compound as claimed in claim
 1. 7. A method oftreatment of atopic or non-atopic dermatitis, Crohn's disease,ulcerative colitis, or irritable bowel disease, comprising administeringto a patient suffering such disease an effective amount of a compound asclaimed in claim
 1. 8. (canceled)